A wireless power transfer system includes a power transmission coil device and a power reception coil device, and implements wireless power transmission using electromagnetic induction, magnetic resonance or the like between coils. For example, the wireless power transfer system is applied to a power feeding system for an electric vehicle or a plug-in hybrid vehicle. In this case, the power reception coil device is installed in a vehicle.
Meanwhile, the power transmission coil device is installed in a parking space or the like. For example, as illustrated in Patent Document 1, the power transmission coil device includes a core. The core described in Patent Document 1 includes a winding core portion around which an electric wire is wound, and a protrusion disposed to be separated from the winding core portion in a winding axis direction of a coil. Both the winding core portion and the protrusion are made of a magnetic material, and a part therebetween is to a discontinuous portion, that is, a space in which the core is not present. The protrusion described in Patent Document 1 is provided to reduce a leakage magnetic field in the winding axis direction.